To aid clarity and to avoid prolixity the present invention will be described herein with respect to pruning in grape vineyard operations for which the present invention has particular application. However, it should be appreciated that the principles of the present invention may find use in other applications (for example, as described more fully below) and thus reference herein to vineyard pruning should not be seen to be limiting.
As part of annual maintenance of grapevines it is necessary to remove old, weak, diseased, non-productive or otherwise unsuitable “cordons” or “canes” of the grapevine. A “cordon” or “cane” refers to a branch of a woody plant to be pruned or left to bud.
Single plants can be pruned to have single or multiple cordons/canes in a number of methods. The two most prominent methods of pruning are known as “spur-pruning” and “cane-pruning” which suit different types of terroir and grape varieties.
Spur-pruning can be used on any variety but is ideally suited to grape varieties that are fruitful in the bud area near the trunk of the vine. Any shoots growing near the trunk are removed and the vine pruned such that the vine consists of a series of ‘spurs’ growing from the cordons which are wrapped about a fruiting wire, i.e. a fixed wire to which the cordons are attached. Thus, spur-pruning results in an array of spurs projecting from the cordons at regular distances from the trunk. The spurs are cut back each year to produce new shoots which bear fruit.
Cane-pruning is described more fully below and is typically used on varieties where the buds closest to the trunk are unfruitful or whose bunches are small. Cane-pruning leaves a select few canes each year extending from the trunk to act as the ‘fruiting wood’. This selection ensures all the nutrients and energy of the vine are taken up by the select canes and thus promotes a full crop from the selected canes over a shorter time-period. In contrast a vine “spur-pruned” spreads the nutrients and energy over multiple spurs over the growing season.
Spur-pruning produces a relatively greater yield in consistent growing conditions over the season but can result in low yield or quality where conditions are variable or the grape variety is generally low-yielding. For example, frosts may result in poor growth on the closest spurs to the trunk while summer drought may result in poor growth on the outer spurs later in the season. In contrast, cane-pruning ensures most shoots grow simultaneously with all the nutrients and energy being available to the shoots over the season. Thus, while spur-pruning can be used in many climates, the highly variable weather conditions in New Zealand and many other regions require cane-pruning to ensure adequate harvest.
“Cane-pruning” or “cordon-pruning” of unwanted canes from grapevines is a labour intensive operation and can be broken down into four distant tasks as follows:
“Cordon Selection”
The first stage of cane-pruning involves “pre-cutting” to select and cut the unwanted canes away from the head of the vine leaving a number of canes selected with the attributes of:                originating from an area close to the head or crown of the vine;        full length and not stunted;        undamaged and free of disease;        golden brown in colour;        having a sufficient number of healthy buds;        sufficient thickness, e.g. thick or thicker than a human finger.        
The cane selection stage is performed manually by a skilled laborer as the selection of appropriate canes can have a high impact on the short and long term productivity of a mature vine.
“Cutting the Unwanted Cane”
The unwanted canes are then cut from the fruiting wire to which they were wrapped about during the previous season's pruning. This cutting makes manual ‘stripping’ of the cut canes easier. This further cutting process is relatively unskilled compared with the cane selection and is usually performed in tandem with cane selection.
“Stripping Out”
The unwanted canes make up about 90% of the total growth on a mature vine and are often tangled in amongst the foliage, wires or other canes, thereby preventing them from falling away from the vine once cut. These unwanted canes must be removed manually in a process referred to as “stripping-out”. Stripping-out generally involves a person gripping the unwanted canes and ripping them away from the vine and wires in a downward motion. Stripping-out can be physically demanding and time consuming. Moreover, stripping-out may also be hazardous when canes are ripped free of the vine as they may whip the person in the face and eyes.
“Trimming and Wrapping”
Once the stripping-out is complete the remaining canes are trimmed to length and shape and wrapped on to the fruiting wire ready for the next growing season. These processes are also done manually and while trimming is generally unskilled, wrapping requires skilled labour.
Thus, cane-pruning of grapevines is a labour-intensive process that has a number of sub-processes requiring skilled workers.
Spur pruning is a faster and less-skilled hand-pruning technique than cane-pruning as there is no selection stage and the spurs are simply pruned back to the required length. The relative simplicity of spur-pruning means that cutting machines can be used to run along the vine and cut the spurs back to a consistent level. In contrast, cane-pruning leaves unwanted canes wrapped about the fruiting wire and thus the cutting techniques of the spur-pruning machines may cut the fruiting wire and/or may not adequately remove the canes.
While a number of machines have been developed to alleviate the heavy manual requirement of spur-pruning grapevines, there has been little development in machines for cane-pruning given the high-skill requirement.
One attempt at reducing at least some of the labour component of cane-pruning has been devised by Walter Langlois1 and involves locating two contra-rotating vehicle-tyres in a confronting relationship either side of the row of vines. The tyres are positioned above the wires such that the tyres grip the upper portions of the unwanted canes and pull them from the wires. The tyres are attached to the boom of a tractor or the like which can then move along the row of vines. 1 Perfecting art of stripping, The Dominion Post (NZ), 16 Aug. 2007.
While the Langlois machine does offer a mechanical alternative to manual stripping of the canes, there are a number of problems that may arise in operation. For example:                the tyres must be lifted over each post along the row of vines thereby reducing speed and efficiency;        the rotating tyres rip the canes from the wire with substantial force, thereby potentially damaging any uncut canes or detaching the fruiting wire from the posts;        the stripped canes are ejected upwards from the tyres at substantial speed, and these may land on the tractor, personnel, other vines or otherwise prove inconvenient and unsightly;        the canes are required to extend above the wire to be effectively stripped which means conventional “pre-pruning” or “summer” pruning must be reduced.        
Typical prior art wire strippers are also unsuitable as they cannot be used to strip cut canes of grapevines, other organic material or any inherently irregular material that grows on the line. It is inherently difficult to ensure that all of the material on the line is stripped as the prior art wire strippers rely on the material and line being fixed in position and dimensions, or alternatively rely on the wire stripper blades moving to accommodate any irregularity.
It would therefore be advantageous to provide an improved method and apparatus for stripping the unwanted canes from the fruiting wire.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein; this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.